1. Field of the Invention
The present invention relates to a sheet material thickness detection device, a sheet material anomaly detection device, a sheet material feeding device, and an image forming device.
2. Description of the Related Art
Sheet material thickness detection devices each for detecting the thickness of a sheet material such as paper in an image forming device, for example, have been conventionally known.
Japanese Unexamined Patent Application Publication No. 2014-031275, for example, discloses a reference roller and a displacement roller arranged to sandwich and convey a sheet material, and a sheet material thickness detection device that detects a difference between displaced amounts of a rotary shaft of the displacement roller in the presence and absence of the sheet material and calculates the thickness of the sheet material on the basis of the detection result.
In the sheet material thickness detection device described in Japanese Unexamined Patent Application Publication No. 2014-031275 above, however, if the device has a machining error (eccentricity or deviation from a perfect circle) that causes a change in distance between an outer periphery and the rotary shaft of the displacement roller depending on a rotation angle, the thickness of a sheet material may not be detected with high accuracy. If the displacement roller is positioned at a rotation angle at which the distance between a portion of the outer periphery of the displacement roller in contact with the sheet material and the rotary shaft is larger than a machining desired dimension, for example, the displaced amount of the rotary shaft of the displacement roller becomes large apparently. Thus, the thickness of the sheet material is calculated to be thicker than its actual thickness, failing to detect the thickness of the sheet material with high accuracy. In order to improve the detection accuracy of the thickness of a sheet material, an expensive displacement roller having less machining error is required. Thus, reduction in cost is difficult to achieve.